[llvm] r320786 - Disabling r312514 as it causes miscompiles that show up on bootstrap

[Nemanja Ivanovic via llvm-commits]

Author: nemanjai
Date: Thu Dec 14 17:38:03 2017
New Revision: 320786

URL: http://llvm.org/viewvc/llvm-project?rev=320786&view=rev
Log:
Disabling r312514 as it causes miscompiles that show up on bootstrap

The compare elimination peephole introduced in https://reviews.llvm.org/rL312514
causes a miscompile in AMDGPUInstrInfo.cpp which in turn causes some AMDGPU
test case failures in stage2 bootstrap testing. This miscompile didn't cause any
test case failures until https://reviews.llvm.org/rL320614, so it appeared as if
that patch caused these failures.
Disabling this transformation for now to bring the build bots back to green and
the author of the patch will investigate the miscompile.

Modified:
    llvm/trunk/lib/Target/PowerPC/PPCMIPeephole.cpp
    llvm/trunk/test/CodeGen/PowerPC/cmp_elimination.ll

Modified: llvm/trunk/lib/Target/PowerPC/PPCMIPeephole.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/PPCMIPeephole.cpp?rev=320786&r1=320785&r2=320786&view=diff
==============================================================================
--- llvm/trunk/lib/Target/PowerPC/PPCMIPeephole.cpp (original)
+++ llvm/trunk/lib/Target/PowerPC/PPCMIPeephole.cpp Thu Dec 14 17:38:03 2017
@@ -729,7 +729,7 @@ bool PPCMIPeephole::simplifyCode(void) {
   // Eliminate all the TOC save instructions which are redundant.
   Simplified |= eliminateRedundantTOCSaves(TOCSaves);
   // We try to eliminate redundant compare instruction.
-  Simplified |= eliminateRedundantCompare();
+  //Simplified |= eliminateRedundantCompare();
 
   return Simplified;
 }

Modified: llvm/trunk/test/CodeGen/PowerPC/cmp_elimination.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/cmp_elimination.ll?rev=320786&r1=320785&r2=320786&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/cmp_elimination.ll (original)
+++ llvm/trunk/test/CodeGen/PowerPC/cmp_elimination.ll Thu Dec 14 17:38:03 2017
@@ -1,3 +1,4 @@
+; XFAIL: *
 ; RUN: llc -verify-machineinstrs < %s -mtriple=powerpc64-unknown-linux-gnu | FileCheck %s
 ; RUN: llc -verify-machineinstrs < %s -mtriple=powerpc64le-unknown-linux-gnu | FileCheck %s